The invention relates to an apparatus for the variable setting of control times of gas-exchange valves of an internal combustion engine with an inner rotor and an outer rotor, which is arranged so that it can rotate relative to the inner rotor, wherein the inner rotor has a constant phase relationship to a crankshaft of the internal combustion engine, wherein the apparatus has one or more coupling elements, in which a drive shaft of an auxiliary assembly can engage, and wherein torque can be transmitted from the apparatus to the drive shaft by the coupling element or coupling elements. In addition, the invention relates to an internal combustion engine with an apparatus for the variable setting of control times of gas-exchange valves and an auxiliary assembly, which is driven by a drive shaft by the apparatus.
It is generally known to someone skilled in the art of automotive engineering that, in addition to a plurality of assemblies, modern internal combustion engines are also equipped with an apparatus for the variable setting of control times of gas-exchange valves (camshaft adjuster), for example, an apparatus for the hydraulic rotational angle adjustment of the camshaft relative to the crankshaft, in order to be able to continuously change the opening and closing times of the gas-exchange valves of the internal combustion engine. In addition, auxiliary assemblies are provided, which are driven by the control drive of the internal combustion engine. Such auxiliary assemblies can be, for example, vacuum pumps for servo loads, for example, in order to generate the negative pressure necessary for a power brake booster of a motor vehicle.
The apparatuses typically used for rotational angle adjustment are here constructed, in principle, as a hydraulic adjustment drive, which is constructed either as a so-called axial-piston adjuster or similar to the apparatus known from EP 0 818 609 B1 as a so-called rotary piston adjuster. This apparatus is arranged on the drive-side end of the camshaft supported by several radial bearings in the cylinder head of the internal combustion engine and is made essentially from a drive unit in driven connection with the crankshaft of the internal combustion engine and from a driven unit locked in rotation with the camshaft of the internal combustion engine. The driven unit is here actually constructed as a vane wheel (called inner rotor below) and is attached to the camshaft by an axial central screw. The drive unit is constructed as a hollow cylinder (called outer rotor below) surrounding the driven unit, wherein this arrangement can be sealed tight against pressurized medium by two axial side walls. Through several radial limiting walls constructed on the outer rotor and several radial vanes constructed on or attached to the inner rotor, two pressure chambers, which can be charged selectively or simultaneously with a hydraulic pressurized medium and by which the outer rotor is connected in a force-transmitting way to the inner rotor, is formed between two limiting walls within the apparatus. Here, as a hydraulic pressurized medium for the apparatus, the lubricating oil of the internal combustion engine transmitted from one of the radial bearings of the camshaft or an oil distributor is used, which is fed by radial and axial oil channels to the apparatus.
Alternatively, the inner rotor can also be in driven connection with the crankshaft and the outer rotor can be locked in rotation with the camshaft. In another alternative embodiment, it can be provided that a first shaft is driven on one end, for example, by a chain, belt, or gearwheel, by the crankshaft. On the other end of this first shaft, a camshaft adjuster can be arranged, wherein the inner rotor is locked in rotation with the camshaft. In this case, a second shaft can be in driven connection, for example, by a chain, belt, or gearwheel, with the outer rotor of the camshaft adjuster, wherein this outer rotor can rotate relative to the inner rotor. Here, the first shaft can involve, for example, an intake camshaft (exhaust camshaft) and the second shaft can involve an exhaust camshaft (intake camshaft). In this case, the control times of the intake camshaft (exhaust camshaft) are selected as fixed times. The control times of the other camshaft, however, can be varied by the camshaft adjuster.
In contrast, the vacuum pumps typically used in internal combustion engines for a servo load are usually constructed as vane cell pumps, like those, for example, from DE 85 18 157 U1. This vacuum pump is arranged on a common longitudinal axis with the camshaft in the cylinder head of the internal combustion engine and is made essentially from a housing arranged stationary relative to the cylinder head or cylinder head cover of the internal combustion engine with a bearing journal and from a rotor arranged in the housing with a drive shaft, which is supported so that it can rotate in the bearing journal of the housing extending into the cylinder head of the internal combustion engine. Here, in the end side of the drive shaft, two recesses are machined, in which two coupling tabs formed on the end side of the camshaft engage and thus transfer the rotational movement of the camshaft to the drive shaft of the vacuum pump. In addition, the camshaft also has an axial lubricating oil channel, which leads to its end side and which is connected, on one side, via a coupling tube to an axial lubricating oil collection space in the drive shaft of the vacuum pump and, on the other side, to the lubricating oil circuit of the internal combustion engine, so that the vacuum pump is also lubricated with the lubricating oil of the internal combustion engine.
In DE 102 60 546 A1, an internal combustion engine is described, which is equipped both with an apparatus for the variable setting of the control times of gas-exchange valves and also with an auxiliary assembly. The auxiliary assembly, in this case a vacuum pump, is equipped with a drive shaft, which is locked in rotation by a coupling with the outer rotor or with components locked in rotation with the outer rotor. In addition, the auxiliary assembly is provided with lubricant by a connection tube via a channel constructed within the central screw.
This attachment of the drive shaft to the outer rotor or to components fixed to the outer rotor has proven to be disadvantageous for embodiments, in which the inner rotor is in a fixed phase relationship relative to the crankshaft of the internal combustion engine. In these embodiments, the inner rotor rotates with half the rotational speed of the crankshaft, wherein a fixed phase relationship is maintained. An outer rotor that can rotate relative to the inner rotor has no fixed phase relationship relative to the crankshaft during an adjustment process of the apparatus. Depending on the direction of adjustment, the outer rotor is temporarily accelerated or decelerated. In the case of a rotationally fixed connection between the outer rotor and the drive shaft of the auxiliary assembly, first, in this way, undesired rotational irregularities are fed via the drive shaft into the auxiliary assembly. Another serious disadvantage comes from the higher moment of inertia of the component to be adjusted. In this embodiment, because the component to be adjusted, the outer rotor, is connected rigidly to the drive shaft and thus, for example, to the rotor of a vane cell pump, during the adjustment process a significantly increased moment of inertia must be accelerated. This leads to a considerable reduction of the adjustment speed and the response behavior of the camshaft adjuster and thus, among other things, to increased emission values, lower power, and lower torque from the internal combustion engine.
Another disadvantage is the lubricant supply from the camshaft adjuster to the auxiliary assembly via components rotating relative to each other (central screw fixed to the inner rotor and drive shaft of the auxiliary assembly fixed to the outer rotor).